Data is transmitted over a network through paths in digital data packets that traverse routers in the network to arrive at a desired destination over IP protocols. Often, data streams must be delivered from a public network to a local node or device in a private network and vice versa. In these situations, any IP-based services are delivered to or from a local node or device through an entry or exit point of a local network. This entry/exit point functions as a gateway for data such that the public network recognizes a single address for the private network. Typically, Network Address Translation (NAT) is employed to present the private network to the Internet or other public network with one address. In this way, the NAT translates individual IP addresses for each device in the private network for the public network such that the private individual IP addresses are concealed from the public network. This results in conservation of addresses and added efficiency of the network interfaces.
Messages or data being transmitted in networks contain a header and payload. The header is the portion of a message or data that contains information that guides the message to the intended destination. Information contained in the header may include the address of the sender, the address of the receiver, precedence level, routing instructions, etc. Transmitted messages or data further contain a payload portion. The payload portion is in the data portion of the IP packet. An interface between the private network and the public network or Internet must know the mapping between a local node or device and its specific IP address and User Data Protocol (UDP) port to correctly route data to the proper destination. The Network Address Translation (NAT) at the gateway is such an interface. It establishes the said mapping between the private and public networks to interpret address data in the IP headers and delivers any incoming data to the desired local node or device.
However, VoIP protocols sometimes contain address information in the payload (i.e., data portion of the IP packet). One example of such a VoIP protocol is MGCP/NCS (Media Gateway Controller Protocol/Network-based Call Signaling protocol). MGCP/NCS protocol is used for call processing signaling control to provide Voice-over-IP (VoIP) services. In situations where specific IP address information and/or port number information is contained in the payload, the NAT, which only interprets data in the IP header, is unable to properly translate the address information or port number information. As a result, data is not properly delivered to the desired destination in the private network.
Further, the actual voice stream is carried by the Real-Time Transport Protocol (RTP). The IP address and port number information for the RTP packets are defined by the Session Description Protocol (SDP) included in the MGCP/NCS payload and need to be translated properly. In addition, the voice stream, i.e., the RTP packets, need to be routed properly to the intended destination. Therefore, the mapping information is necessary at the gateway for proper routing of data to the correct final destination within the private network. The data packet is delivered to the gateway of the private or local network and the gateway must then route the data to the intended destination within the private or local network. The NAT does not have address mapping information and therefore cannot properly route data to the desired destination node.
Therefore, there exists a need in the art to properly translate address and/or port number information such that VoIP signaling packets are delivered to the desired destination node within a private or local network and public network.
Further, there exists a need in the art to provide address mapping information and actually perform the routing if necessary for delivery of VoIP voice packets to the desired destination node within a private or local network and public network.